Conventional display device, and particularly, those used for image conversion, include the combination of a photoconductive material such as CdS and an electroluminescent element, or a photoconductive material in combination with a transparent ceramic. However, each of these combinations is less than ideal. For example, so far as the combination of the photoconductive material and the electroluminescent element is concerned, the voltage required for operation is high and the luminous efficiency is low. With respect to the display device incorporating a transparent ceramic, the cost of manufacture of the transparent ceramic is high and the size range is narrow, because it is impossible to make a large element of this type.
As is apparent, then, there is need for a display device useful as an image converter and as a memory device, where the display device can be of large size and present an image with fine detail and in high contrast.